1. Field of the Invention
The present invention relates to a honeycomb structure and a method for manufacturing a honeycomb structure.
2. Discussion of the Background
In recent years, particulates (hereinafter, also referred to as PM) such as soot and other toxic components contained in exhaust gases discharged from internal combustion engines of vehicles such as buses and trucks, and construction machines have raised serious problems as contaminants harmful to the environment and the human body.
For this reason, various honeycomb structures made from porous ceramics have been proposed as honeycomb filters that capture PM in exhaust gases and purify the exhaust gases, and also as catalyst supporting carriers that allow exhaust gases to pass through the inside thereof to convert the exhaust gases.
As a honeycomb structure of this kind, a honeycomb structure manufactured by combining a plurality of honeycomb fired body is known, and in JP2004-154718A, a honeycomb structure formed by combining a plurality of kinds of honeycomb fired bodies having different shapes has been disclosed.
FIG. 1 is a perspective view schematically showing one example of the honeycomb structure manufactured by combining a plurality of kinds of honeycomb fired bodies having different shapes.
A honeycomb structure 300 shown in FIG. 1 is a honeycomb structure in which a plurality of honeycomb fired bodies 310, 320, and 330, having different shapes, are combined with one another by interposing an adhesive layer 301 to form a round pillar-shaped ceramic block 303 and a sealing material layer 302 is further formed on a peripheral face 304 of the ceramic block 303.
FIG. 2A is a perspective view schematically showing one example of a honeycomb fired body forming the honeycomb structure, and FIG. 2B is a cross-sectional view taken along line A-A of FIG. 2A.
A honeycomb fired body 330 is, out of honeycomb fired bodies forming the honeycomb structure, a virtually rectangular pillar-shaped honeycomb fired body placed inside the honeycomb structure.
In the honeycomb fired body 330, a large number of cells 331 are disposed in parallel with one another with a cell wall 333 therebetween in the longitudinal direction (the direction shown by an arrow a in FIG. 2A), and either one end of each of the cells 331 is sealed by plug material 332. Therefore, exhausted gases G flowing into one cell 331 with an opening on one end face are to be discharged from another cell 331 with an opening on the other end face after passing through a cell wall 333 between the cells 331.
Consequently, the cell wall 333 is allowed to function as a filter to capture PM and the like.
FIGS. 3A and 3B are perspective views schematically showing examples of a honeycomb fired body placed at an outermost periphery of the honeycomb structure, out of the honeycomb fired bodies forming the honeycomb structure.
In honeycomb fired bodies 310, 320 shown in FIGS. 3A and 3B, a plurality of cells 311, 321 are disposed in parallel with one another in the longitudinal direction, and cells 311, 321 are separated by cell walls 313, 323. Consequently, the cell walls 313, 323 of the honeycomb fired bodies 310, 320 are allowed to function as filters to capture PM and the like.
Here, shapes of the cells 311, 321 of the honeycomb fired bodies 310, 320 are all virtually quadrate shapes.
The cells 311, 321 of the honeycomb fired bodies 310, 320 are surrounded by outer walls 315, 325 and the cells are not exposed from a side face of the honeycomb fired bodies.
Further, out of the outer walls 315, 325 located outside the cells of the honeycomb fired bodies 310, 320 and not separating the cells, outer walls 316, 326, each of which is to be a peripheral face (see FIG. 1) of a ceramic block, form curved side faces.
In the present description, out of the outer walls forming side faces of the honeycomb fired bodies, an outer wall which is to be a peripheral face of the ceramic block is referred to as a peripheral wall.
Further, a cell in contact with the peripheral wall of the honeycomb fired body is referred to as a cell located at an outermost periphery.
A ceramic block 303 manufactured by placing the honeycomb fired bodies 310 and 320 at the outermost periphery has a smooth round pillar-shaped peripheral face 304. By forming a sealing material layer 302 on the peripheral face 304 of the ceramic block 303, the round pillar-shaped honeycomb structure 300 can be obtained.
The contents of JP2004-154718A are incorporated herein by reference in their entirety.